Fix warnings for -Wall -Wextra

This commit fixes all warnings when the -Wall -Wextra compiler
options are provided. Tested with Clang and GCC.

hashmap.c

@@ -87,7 +87,7 @@ struct hashmap *hashmap_new_with_allocator(
     _malloc = _malloc ? _malloc : malloc;
     _realloc = _realloc ? _realloc : realloc;
     _free = _free ? _free : free;
-    int ncap = 16;
+    size_t ncap = 16;
     if (cap < ncap) {
         cap = ncap;
     } else {
@@ -504,12 +504,12 @@ static uint64_t SIP64(const uint8_t *in, const size_t inlen,
     const int left = inlen & 7;
     uint64_t b = ((uint64_t)inlen) << 56;
     switch (left) {
-    case 7: b |= ((uint64_t)in[6]) << 48;
-    case 6: b |= ((uint64_t)in[5]) << 40;
-    case 5: b |= ((uint64_t)in[4]) << 32;
-    case 4: b |= ((uint64_t)in[3]) << 24;
-    case 3: b |= ((uint64_t)in[2]) << 16;
-    case 2: b |= ((uint64_t)in[1]) << 8;
+    case 7: b |= ((uint64_t)in[6]) << 48; /* fall through */
+    case 6: b |= ((uint64_t)in[5]) << 40; /* fall through */
+    case 5: b |= ((uint64_t)in[4]) << 32; /* fall through */
+    case 4: b |= ((uint64_t)in[3]) << 24; /* fall through */
+    case 3: b |= ((uint64_t)in[2]) << 16; /* fall through */
+    case 2: b |= ((uint64_t)in[1]) << 8; /* fall through */
     case 1: b |= ((uint64_t)in[0]); break;
     case 0: break;
     }
@@ -564,25 +564,29 @@ static void MM86128(const void *key, const int len, uint32_t seed, void *out) {
     uint32_t k3 = 0;
     uint32_t k4 = 0;
     switch(len & 15) {
-    case 15: k4 ^= tail[14] << 16;
-    case 14: k4 ^= tail[13] << 8;
+    case 15: k4 ^= tail[14] << 16; /* fall through */
+    case 14: k4 ^= tail[13] << 8; /* fall through */
     case 13: k4 ^= tail[12] << 0;
              k4 *= c4; k4  = ROTL32(k4,18); k4 *= c1; h4 ^= k4;
-    case 12: k3 ^= tail[11] << 24;
-    case 11: k3 ^= tail[10] << 16;
-    case 10: k3 ^= tail[ 9] << 8;
+             /* fall through */
+    case 12: k3 ^= tail[11] << 24; /* fall through */
+    case 11: k3 ^= tail[10] << 16; /* fall through */
+    case 10: k3 ^= tail[ 9] << 8; /* fall through */
     case  9: k3 ^= tail[ 8] << 0;
              k3 *= c3; k3  = ROTL32(k3,17); k3 *= c4; h3 ^= k3;
-    case  8: k2 ^= tail[ 7] << 24;
-    case  7: k2 ^= tail[ 6] << 16;
-    case  6: k2 ^= tail[ 5] << 8;
+             /* fall through */
+    case  8: k2 ^= tail[ 7] << 24; /* fall through */
+    case  7: k2 ^= tail[ 6] << 16; /* fall through */
+    case  6: k2 ^= tail[ 5] << 8; /* fall through */
     case  5: k2 ^= tail[ 4] << 0;
              k2 *= c2; k2  = ROTL32(k2,16); k2 *= c3; h2 ^= k2;
-    case  4: k1 ^= tail[ 3] << 24;
-    case  3: k1 ^= tail[ 2] << 16;
-    case  2: k1 ^= tail[ 1] << 8;
+             /* fall through */
+    case  4: k1 ^= tail[ 3] << 24; /* fall through */
+    case  3: k1 ^= tail[ 2] << 16; /* fall through */
+    case  2: k1 ^= tail[ 1] << 8; /* fall through */
     case  1: k1 ^= tail[ 0] << 0;
              k1 *= c1; k1  = ROTL32(k1,15); k1 *= c2; h1 ^= k1;
+             /* fall through */
     };
     h1 ^= len; h2 ^= len; h3 ^= len; h4 ^= len;
     h1 += h2; h1 += h3; h1 += h4;
@@ -607,6 +611,7 @@ uint64_t hashmap_sip(const void *data, size_t len,
 uint64_t hashmap_murmur(const void *data, size_t len, 
                         uint64_t seed0, uint64_t seed1)
 {
+    (void)seed1;
     char out[16];
     MM86128(data, len, seed0, &out);
     return *(uint64_t*)out;
@@ -629,9 +634,12 @@ static size_t deepcount(struct hashmap *map) {
     return count;
 }
 
-
-#pragma GCC diagnostic ignored "-Wextra"
-
+#ifdef __GNUC__
+#pragma GCC diagnostic ignored "-Wunused-parameter"
+#endif
+#ifdef __clang__
+#pragma GCC diagnostic ignored "-Wcompound-token-split-by-macro"
+#endif
 
 #include <stdlib.h>
 #include <string.h>
@@ -682,10 +690,6 @@ static bool iter_ints(const void *item, void *udata) {
     return true;
 }
 
-static int compare_ints(const void *a, const void *b) {
-    return *(int*)a - *(int*)b;
-}
-
 static int compare_ints_udata(const void *a, const void *b, void *udata) {
     return *(int*)a - *(int*)b;
 }
@@ -731,7 +735,7 @@ static void all() {
     shuffle(vals, N, sizeof(int));
     for (int i = 0; i < N; i++) {
         // // printf("== %d ==\n", vals[i]);
-        assert(map->count == i);
+        assert(map->count == (size_t)i);
         assert(map->count == hashmap_count(map));
         assert(map->count == deepcount(map));
         int *v;
@@ -766,7 +770,7 @@ static void all() {
         assert(!hashmap_get(map, &vals[i]));
         assert(!hashmap_delete(map, &vals[i]));
         assert(!hashmap_set(map, &vals[i]));
-        assert(map->count == i+1);
+        assert(map->count == (size_t)(i+1));
         assert(map->count == hashmap_count(map));
         assert(map->count == deepcount(map));
     }
@@ -793,7 +797,7 @@ static void all() {
         v = hashmap_delete(map, &vals[i]);
         assert(v && *v == vals[i]);
         assert(!hashmap_get(map, &vals[i]));
-        assert(map->count == N-i-1);
+        assert(map->count == (size_t)(N-i-1));
         assert(map->count == hashmap_count(map));
         assert(map->count == deepcount(map));
         for (int j = N-1; j > i; j--) {